Power semiconductor devices conduct a high load current and withstand a high blocking voltage. Superjunction devices include a superjunction structure with oppositely doped first and second regions formed in a drift zone which is electrically arranged in series to controllable MOSFET channels. When a blocking voltage is applied to the superjunction device, a lateral electric field rises and clears out the mobile charge carriers along the vertical pn junctions between the first and second regions. A space charge zones begins to expand perpendicularly to the direction of a load current flow in the on-state. The mobile charge carriers are completely forced out of the superjunction structure at a comparatively low blocking voltage. When the blocking voltage is further increased, the depleted superjunction structure acts as a quasi-intrinsic layer and the vertical electric field rises.
The breakdown voltage is decoupled from the dopant concentrations in the superjunction structure such that the dopant concentration in the superjunction structure can be comparatively high. Therefore superjunction devices typically combine very low on-state resistance with high blocking capability. The efficiency of the superjunction structure in terms of blocking capability and semiconductor volume is the better the better the dopant atoms in the oppositely doped regions of the superjunction structure are balanced and compensate each other.
It is desirable to improve superjunction semiconductor devices.